from collections import Counter

c = Counter()
print('Initial : ', c)

c.update('abcdaab')
print('Sequence : ', c)

c.update({'a': 1, 'd': 5})
print('Dict :', c)

# 不存在的元素会返回0
for letter in 'abcde':
    print('{} : {}'.format(letter, c[letter]))
